Method for producing high-purity nickel

ABSTRACT

A method for producing high-purity nickel, which involves using a hydrochloric acid solution system to electro-deposit high-purity nickel, characterized in that, it includes the following steps sequentially: 3N-grade-grade electrolytic nickel was used as anode and the electro-deposition was carried out in a hydrochloric acid system, the solution obtained from the electro-deposition was extracted by a three-level countercurrent extraction using anion extraction solvents, and then back-extracted and degreased. After that, the solution was passed through the anion exchange resin to be further purified by ion exchange, and finally put into the electrolytic cell to deposit nickel. The amount of the solution that was put into the cell and the amount of the solution that was drawn out of the cell after the electro-deposition was the same? After the glow discharge analysis by a mass spectrography, the high-purity nickel obtained by the method according to the present invention was the 5N-grade-grade high-purity nickel. The cost was low and the contamination was prevented.

FIELD OF THE INVENTION

The present invention relates to a method for producing nickel. More particularly, it relates to a method for producing high purity nickel that includes employing 3N-grade electrolytic nickel to electro-deposited in hydrochloric acid solution system.

BACKGROUND OF THE INVENTION

Large quantities of special materials are demanded with the development of high technology. Many types of high purity metal which have been found are used for Hi-tech strategic goods. The production, application and characters of the high-purity or super high-purity metals are novel and growing in modern material science and engineering field. High-purity (purer than 5N-grade) metals are used in producing semiconductor and VLSI widely. More than 20 types of high purity metal such as Ga, In, As, Sb, Cd, Sn, Te, Bi, S, Zn, Cu, Se, P and their compounds or alloys are used to produce electronic components and PCB.

Nickel is generally used in the conventional stainless steel, alloy and other fields. In recent years, demand of high purity nickel increased in several special fields. For example, a superalloy made of high purity nickel sis applied in aeroengines, protective materials for nuclear reactor, biomaterials and low-expansion alloys; Consumption of high purity nickel gradually increases in electronic industry field. For example, a specific Ni—Fe alloy is applied in lead frame, and a Cu—Ni—Sn alloy is applied in wire port; It requires very low content of impurities such as alkali metals, radioelements, transition metals and gases, when high-purity nickel is applied in LSI and thereof line material, magnetic membrane, and special packing materials.

The methods for producing high purity nickel have been disclosed in few publications and patents. For example, WO03/014421A1 (title: method for producing high purity nickel, high purity nickel, spattering target comprising the high purity nickel, and thin film formed by using said spattering target) discloses a method for producing high purity nickel by employing soluble nickel as an anode and bagging the cathode with membrane, removing impurities through depositing them as hydroxide, preliminary electrolyzing or displacing them by displacement reaction by adding nickel foil to the electrolytic solution, purifying electrolytic solution, then electrolyzing to produce high purity nickel of 5N-grade (99.999%). Main impurities of the produced nickel can be follows: O less then 30 ppm, C, N, S, P and F less than 10 ppm each. (the concentrations of other impurities haven't been disclosed.)

Moreover, JP P2000-219988A (title: method for producing high purity nickel and high purity nickel for forming metallization film) discloses a method for producing high purity nickel by performing electrolysis with a soluble anode, and the anode and cathode are partitioned with two-layer membrane, employing anion exchange resin to eliminate the impurities in electrolytic solution, lower the concentration of hydrochloric acid in the electrolytic solution by diffusion dialysis or evaporation drying, purifying the electrolytic solution and then electrolyzing to obtain the high purity nickel. The high purity nickel produced by this method has fewer impurities. Main impurities of the produced nickel can be follows: alkali metals less than 1 ppm, Fe, Co, Cr less than 10 ppm each, U and Th less than 1 ppb each, C less than 50 ppm, and O less than 100 ppm.

To overcome the problem about the high acid of electric dissolving stock solution. Boiling and adding alkali to reduce the acid content are broadly applied in the current methods for producing high purity nickel, but the said methods result in a high cost and pollution, and the solution may not be completely purified. High concentration of impurities in high purity nickel is caused by the mixing of anolyte and catolyte, due to the adoption of a soluble anode.

SUMMARY OF THE INVENTION

On a basis of the foresaid existed technological deficiencies, the object of the present invention is to provide a method for producing high purity nickel to settle effectively high concentration of acid in the electric dissolving stock solution cut down on production cost, dispel pollution, and depurate solution, and prevent the anolyte and catolyte from mixing each other.

An object of the present invention is to provide a method for producing high purity nickel. The said method involves the following steps:

a. Employing 3N-grade electrolytic nickel as anode and corrosion resistant titanium wire as cathode, electrolyzing in hydrochloric acid system are electrolyse to prepare NiCl₂ solution at the current density of about 100 A/m² to 200 A/m²; and at the end of electrolysis when the concentration of H⁺ is about 1 g/l to 2 g/l, electrolyzing at the current density of about 30 A/m² to 70 A/m² to a pH of the solution of about 1 to 3;

b. After degreasing the back-extracted solution through the activated carbon column, then purifying the said solution through ion-exchange column of mixed anion exchange resin of anion exchange resin 331, 717, D301 and D401 at the exchange follow rate equal to or less than 2BV/h. Main impurities of the prepared solution can be follows: Co and Fe less than 0.001 g/l each, and Cu, Pb and Zn less than 0.0002 g/l each; and

c. Electro-depositing in solution purified by ion exchange resin in electrolytic cell at a pH of about 1 to 3, the current density of about 100 A/m² to 200 A/m² and a temperature of about 40 to 60°, drawing out the electro-deposited solution simultaneously to keep a constant circulating to obtain high purity nickel.

A method according to the present invention for producing high purity nickel characterized in that the said electrolytic solution is extracted by 3-stage countercurrent extraction at the extractant phase ratio of 1:2, and back-extract with pure water 10 mins after achieving extraction equilibrium.

A method for producing high purity nickel according to the present invention, characterized in that anion extractant contains 20 vol. % to 40 vol. % tertiary amine, 20 vol. % to 45 vol. % butylate, and sulphonated kerosene.

A method for producing high purity nickel according to the present invention, characterized in that it is performed before extracting NiCl2 solution that purifying the organic phase of the anion extractant by washing and sequentially saturating the said organic phase with 4N high purity hydrochloric acid.

A method for producing high purity nickel according to the present invention characterized in that a hollow fiber ball is employed to degrease the said solution.

A method for producing high purity nickel according to the present invention which employs combined anion exchange resin to form a three dimensional structure to further purify the solution.

A method according to the present invention electro-deposit employs high purity solution purified with ion exchange resin to produce high purity nickel of 5N-grade purity and determined by glow discharge mass spectrometry (GDMS) 5N-grade. In the procedure, reducing the content of acid in the solution by electrolyzing at a low current density at the end of electrolysis procedure, overcome the high concentration of acid in the electrolytic solution, removed acid by boil or neutralization, And it cut down the cost and prevent pollution. It employs high purity hydrochloric acid to saturate the purified organic phase, and then extract the high concentration of NiCl₂ solution with the said organic phase to remove Co in order to purify the solution. It also employs combined anion exchange resin forming a three dimensional structure to further purify the solution. It performs the electrolysis, extraction, ion exchange and electro-deposition continuously to further purify the electrolytic solution. It employs an insoluble anode to produce high purity nickel purer than 5N-grade, so only purified high purity NiCl₂ solution is in the electro-deposition cell. Compared with employing a soluble anode. it prevents the anolyte and catolyte from mixing each other, so that main impurities of the produced high purity nickel can be follows: alkali metals less than 0.1 ppm, Fe, Co, and Cr less than 1 ppm each, U and Th less than 0.1 ppb each, C less than 60 ppm, and O less than 100 ppm.

Detected impurities in the high purity nickel according to the present invention include 16 impurities as Co, Fe, Cu, Zn, As, Cd, Sn, Sb, Pb, Bi, Al, Mn, Mg, Si, P, and S. Concentration of each impurity element is less than 1 ppm and the concentration of the main element nickel is more than 99.999%. Preparation high purity NiCl₂ solution is the basement of producing high purity nickel. Five impracticable elements, Fe, Co, Cu, Pb and Zn, which have been chosen from 16 impurities, are detected as the main impurities. According to the result estimates the purity of the solution. The experiment shows that choosing the typical impurities as the main objects to remove can improve the determining efficiency.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows the process flow diagram of the method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A method for producing high purity nickel involves the sequential steps of:

a. Employing 3N-grade electrolytic nickel as anode and corrosion resistant titanium wire as cathode, electrolyzing in hydrochloric acid system to obtain NiCl₂ solution at the current density of 100-200 A/m²; and at the end of electrolysis when the concentration of H⁺ is 1-2 g/l electrolyzing at the current density of 30-70 A/m² to a pH of the solution of about 1 to 3. Electrolyzing at a low current density at the end of electrolysis procedure, which can lower the content of acid in the solution, and avoid the high concentration of acid in the electrolytic solution. Also, it is less cost and pollution for without removing acid by boil or neutralization. The contents of impurities element in prepared NiCl₂ solution by electrolysis are as follows: 0.006 g/l to 0.009 g/l Co, 0.002 g/l Cu, 0.002 g/l Fe, 0.001 g/l Pb, and 0.002 g/l Zn.

b. The said electrolytic solution is extracted by 3-stage countercurrent extraction with anion extractant which contains 20 vol. % to 40 vol. % tertiary amine, 20 vol. % to 45 vol. % butylate, and sulphonated kerosene, at the extractant phase ratio of 1:2, back-extracted with pure water 10 minutes after achieving extraction equilibrium. Since the concentration of Cl⁻ is increased, the impurities of Fe, Co, Cu, Pb and Zn form complexes anion sufficiently. Fewer impurities exist in the solution after purifying by extracting with anion exctractant, and the main impurities can be follows: Cu and Zn less than 0.0003 g/l each, and Co less than 0.001 g/l.

c. The extracted solution is degreased through the activated carbon column, and further purified the said solution through anion exchange resin 331, 717, D301 and D401 mixed ion-exchange resin sequentially at the exchange follow rate no more than 2 BV/h. The purified solution contains Co and Fe are both less than 0.001 g/l, Cu, Pb and Zn are all less than 0.0002 g/. Since the design principle of ion exchange system is to ensure that no impurities from the system pollute the solution, the pure materials is used to make ion exchange column main body as well as system. The antipollution metering pump is used to transport and control the follow of ion exchange solution quantitatively, and the specific anion exchange resin is used to further purify.

Extracting residue is degreased, adjusted acidity, purified by ion exchange resin at the flow rate of about 1 BV/h to 2 BV/h. Impurities could not be removed efficiently at the too fast flow, and on the contrary, it will deduce the economic efficiency at the too slow flow. The impurities such as Pb, Zn, Cu, Fe, and Co in the solution are reduced after ion exchange and the solution contains 0.006 g/l to 0.009 g/l Co, 0.002 g/l Cu, 0.00 g/l Pb, and 0.002 g/l Zn.

d. The solution purified by ion exchange resin is electro-deposited in electrolytic cell at a pH of about 1 to 3, a current density of about 100 A/m² to 200 A/m² and a temperature of 40 to 60°, draw out the electro-deposited solution simultaneously to keep a constant circulating to obtain high purity nickel, which is analyzed by glow discharge mass spectrometry (GDMS) to achieves 5N-grade purity high purity nickel.

It is required that no pollution from either electrolytic cell or environment exists during the producing high purity experiment. Therefore pure materials are used to make the electrolytic cell. The electrolytic cell is airproofed and has a dustproof head cover which is connect with the cell with water seal. Cathode plate and anode plate assembled with conductive rods are hung on the head cover. Electrode plates and conductive rods are made of pure anticorrosive material to prevent acid corrosion and pollution in solution. Circuit junctions are fastened with screws and high precision silicon rectifier power is employed in order to keep constant electrobath voltage and current and eliminate junction resistance.

EXAMPLES

As hereunder, Examples of the present invention will be illustrated, but the following disclosure shows preferred examples of the present invention only and does not limit the scope of the present invention at all.

Example 1

3N-grade electrolytic nickel was electrolyzed in hydrochloric acid system to prepare NiCl₂ solution at a current density of 100 A/m². When the concentration of H⁺ was 1 g/l, the current density was changed to 30 A/m² and electrolyzed till the pH of the solution to 3, wherein the concentration of Cl⁻ was 6 mol/L and the impurities were shown in the table 1.

TABLE 1 Contents of impurities in original solution unit: g/l No. Name Co Cu Fe Pb Zn 1 original solution 0.009 0.002 0.002 0.001 0.001

Anion extractant contained 25 vol. % tertiary amine, 45 vol. % butylate, and 30 vol. % sulphonated kerosene was washed by high purity water, saturated with 4 mol/l high purity hydrochloric acid. The electrolytic solution was extracted by 3-stage countercurrent extraction at the extractant phase ratio of 1:2, and then back-extracted with pure water 10 minutes after achieving extraction equilibrium. The concentration of Co was decreased from 0.009 g/l to 0.001 g/l. The ingredients of extracting residue were shown in table 2.

TABLE 2 Contents of impurities in extract residue unit: g/l No. Item Co Cu Fe Pb Zn 1 Extract 0.001 0.0003 0.001 0.001 0.0003 residue 2

The back-extracted solution was degreased through activated carbon column, further purified through ion exchange column mixed ion exchange resin from anion exchange resin 331, 717, D301 and D401 at the exchange follow rate of 2 BV/h. Ingredients in solution further purified by ion change were shown in table 3.

TABLE 3 Contents of impurities in purified solution by ion exchange unit: g/l No. Item Co Cu Fe Pb Zn 1 Purified solution <0.0004 0.0001 <0.0004 <0.0001 0.0001 by ion change

Eletrowinning conditions: current density was 100 A/m², pH of NiCl₂ solution was 3, Eletrowinning temperature was 50°. An insoluble anode was employed to electro-deposit the solution further purified by ion exchange to produce 5N-grade high purity nickel. Main impurities of the produced high purity nickel were as follows: alkali metals less than 0.1 ppm, Fe, Co and Cr less than 1 ppm each, U and Th less than 0.1 ppb each, C less than 60 ppm, and O less than 100 ppm. Contents of some impurities in high purity nickel were shown in table 4.

TABLE 4 Impurities in high purity nickel determined by glow discharge mass spectrometry (GDMS) impurities in No. Impurities sample 1 (ppm) 1 Cu <0.8 2 Fe 0.38 3 Co <0.04 4 Pb 0.28 5 Zn <0.03 6 Cd <0.01 7 Bi <0.005 8 Sb 0.14 9 Sn <0.5 10 As <0.8 11 Al 0.02 12 Mg <0.001 13 Mn <0.005 14 Si 0.04 15 P <0.01 16 S 0.1 Total impurities in high purity nickel <3 Contents of nickel (%) >99.9997%

Example 2

3N-grade electrolytic nickel was electrolyzed in hydrochloric acid system to prepare NiCl₂ solution at a current density of 150 A/m². When the concentration of H⁺ was 1.5 g/l, the current density was changed to 50 A/m² and electrolyzed till the pH of the solution to 3, wherein the concentration of Cl⁻ was 6 mol/L and the impurities were shown in the table 5.

TABLE 5 Contents of impurities in original solution unit: g/l No. Item Co Cu Fe Pb Zn 1 original solution 0.008 0.003 0.001 0.001 0.001

Anion extractant contained 40 vol. % tertiary amine, 20 vol. % butylate, and 40 vol. % sulphonated kerosene was washed by high purity water, saturated with 4 mol/l high purity hydrochloric acid. The electrolytic solution was extracted by 3-stage countercurrent extraction at the extractant phase ratio of 1:2, and then back-extracted with pure water 10 minutes after achieving extraction equilibrium. The concentration of Co was decreased from 0.008 g/l to 0.001 g/l. The ingredients of extract residue were shown in table 6.

TABLE 6 Contents of impurities in extract residue unit: g/l No. Item Co Cu Fe Pb Zn 1 Extraction 0.001 0.0002 0.0009 0.001 0.0003 residue 2

The back-extracted solution was degreased through activated carbon column, further purified through ion exchange column mixed ion exchange resin from anion exchange resin 331, 717, D301 and D401 at the exchange follow rate of 1.5 BV/h. Ingredients in solution further purified by ion change were shown in table 7.

TABLE 7 Contents of impurities in solution purified by ion exchange unit: g/l No. Item Co Cu Fe Pb Zn 1 Solution purified <0.0004 0.0001 <0.0004 <0.0001 0.0001 by ion change

An insoluble anode was employed to electro-deposit NiCl₂ solution. Eletrowinning conditions were as follows: current density was 100 A/m², pH of NiCl₂ solution was 3, Eletrowinning temperature was 50°. An insoluble anode was employed to electro-deposit in the solution further purified by ion exchange to produce 5N-grade high purity nickel. Main impurities of the produced high purity nickel were as follows: alkali metals less than 0.1 ppm, Fe, Co, and Cr less than 1 ppm each, U and Th less than 0.1 ppb each, C less than 60 ppm, and O less than 100 ppm. Contents of some impurities in high purity nickel were shown in table 7.

TABLE 7 Impurities in high purity nickel determined by glow discharge mass spectrometry (GDMS) Impurities in No. Impurities sample 1 (ppm) 1 Cu <0.9 2 Fe 0.35 3 Co <0.05 4 Pb 0.45 5 Zn <0.03 6 Cd <0.02 7 Bi <0.005 8 Sb 0.14 9 Sn <0.3 10 As <0.8 11 Al 0.02 12 Mg <0.005 13 Mn <0.005 14 Si 0.05 15 P <0.01 16 S 0.15 Total impurities in high purity nickel <3 Contents of nickel (%) >99.9997%

Example 3

Employed electrolytic solution such as example 2 and the anion extractant contained 20 vol. % tertiary amine, 45 vol. % butylate, and 35 vol. % sulphonated kerosene, Ingredients in solution further purified by ion change were shown in table 8.

TABLE 8 Contents of impurities in solution purified by ion exchange unit: g/l No. Item Co Cu Fe Pb Zn 1 Solution purified <0.0004 0.0001 <0.0004 <0.0001 0.0001 by ion change

An insoluble anode was employed to electro-deposit in NiCI₂ solution. Electro-deposition conditions were as follows: current density was 200 Am², pH of NiCl₂solution was 2. Electro-deposition temperature was 60°. An insoluble anode was employed to electro-deposit the solution further purified by ion exchange to produce 5N-grade high purity nickel. Main impurities of the produced high purity nickel were as follows: alkali metals less than 0.1 ppm, Fe, Co and Cr less than 1 ppm each, U and Th less than 0.1 ppb each, C less than 60 ppm, and O less than 100 ppm. Contents of main impurities in high purity nickel were shown in table 9.

TABLE 9 Impurities in high purity nickel determined by glow discharge mass spectrometry (GDMS) Impurities in No. Impurities sample 2 (ppm) 1 Cu <0.4 2 Fe 0.11 3 Co 0.58 4 Pb 0.28 5 Zn <0.02 6 Cd <0.07 7 Bi <0.005 8 Sb <0.04 9 Sn <1.1 10 As <0.15 11 Al 0.004 12 Mg <0.005 13 Mn <0.005 14 Si <0.005 15 P 0.02 16 S 0.08 Total impurities in high purity nickel <3 Contents of nickel (%) >99.9997%

Example 4

3N-grade electrolytic nickel was electrolyzed in hydrochloric acid system to prepare NiCl₂ solution at a current density of 200 A/m². When the concentration of H⁺ was 2 g/l, the current density was changed to 70 A/m² and electrolyzed till the pH of the solution to 1, wherein the concentration of Cl⁻ was 6 mol/L and the impurities were shown in the table 10.

TABLE 10 Contents of impurities in original solution unit: g/l No. Item Co Cu Fe Pb Zn 1 original solution 0.006 0.002 0.002 0.001 0.001

Then the solution was purified by ion exchange resin at the follow rate of 1 BV/h. Ingredients in solution further was purified by ion change were shown in table 11.

TABLE 11 contents of impurities in solution after ion exchange unit: g/l No. Item Co Cu Fe Pb Zn 1 Solution purified <0.001 0.0002 <0.001 <0.0002 0.0001 by ion change

An insoluble anode was employed to electro-deposit in the high purity NiCl₂ solution. Electro-deposition conditions were as follows: current density was 160 A/m², pH of NiCl₂ solution was 1, Electro-deposition temperature was 50°. An insoluble anode was employed to electro-deposit in the solution and further was purified by ion exchange to produce 5N-grade high purity nickel. Main impurities of the produced high purity nickel were as follows: alkali metals less than 0.1 ppm, Fe, Co and Cr less than 1 ppm each, U and Th less than 0.1 ppb each, C less than 60 ppm, and O less than 100 ppm. Contents of main impurities in high purity nickel were shown in table 12.

TABLE 12 Impurities in high purity nickel determined by glow discharge mass spectrometry (GDMS) Impurities in No. Impurities sample 2 (ppm) 1 Cu 0.38 2 Fe 0.11 3 Co 0.6 4 Pb 0.3 5 Zn <0.02 6 Cd <0.07 7 Bi <0.005 8 Sb <0.04 9 Sn <1.2 10 As 0.13 11 Al 0.004 12 Mg <0.005 13 Mn <0.005 14 Si <0.005 15 P 0.02 16 S 0.08 Total impurities in high purity nickel <3 Contents of nickel (%) >99.9997% 

1. Method for producing high purity nickel, characterized in that it involves the sequential steps: a. Employing 3N-grade electrolytic nickel as anode and corrosion resistant titanium wire as cathode, electrolyzing in hydrochloric acid system are electrolyse to prepare NiCl₂ solution at the current density of about 100 A/m² to 200 A/m²; and at the end of electrolysis when the concentration of H⁺ is about 1 g/l to 2 g/l, electrolyzing at the current density of about 30 A/m² to 70 A/m² to a pH of the solution of about 1 to 3 b. After degreasing the back-extracted solution through the activated carbon column, then purifying the said solution through ion-exchange column of mixed anion exchange resin of anion exchange resin 331, 717, D301 and D401 at the exchange follow rate equal to or less than 2 BV/h. Main impurities of the prepared solution can be follows: Co and Fe less than 0.001 g/l each, and Cu, Pb and Zn less than 0.0002 g/l each; and c. electro-depositing in solution purified by ion exchange resin in electrolytic cell at a pH of about 1 to 3, the current density of about 100 A/m² to 200 A/m² and a temperature of about 40° to 60°, drawing out the electro-deposited solution simultaneously to keep a constant circulating to obtain high purity nickel.
 2. The method for producing high purity nickel according to claim 1, characterized in that the said electrolytic solution is extracted by 3-stage countercurrent extraction at the extractant phase ratio of 1:2, and back-extract with pure water 10 mins after achieving extraction equilibrium.
 3. The method for producing high purity nickel according to claim 1 or 2, characterized in that anion extractant contains 20 vol. % to 40 vol. % tertiary amine, 20 vol. % to 45 vol. % butylate, and sulphonated kerosene.
 4. The method for producing high purity nickel according to claim 1, characterized in that it is performed before extracting NiCl2 solution that purifying the organic phase of the anion extractant by washing and sequentially saturating the said organic phase with 4N high purity hydrochloric acid.
 5. The method for producing high purity nickel according to claim 1, characterized in that a hollow fiber ball is employed to degrease the said solution. 